cptsd on top of chronic major depressive disorder = anxiety time all the time. i wake up in a flat out panic attack regularly.
breathing exercises do help a lot in the moment if one is able to clear their head, which i know is fucking hard for a lot of us. for me it helps to focus on counting the lengths of my breaths out loud or "loudly" in my head while also feeling how deep into my gut i can inhale. some people say they have good luck imagining a happy/relaxing place (beach, forest, sunny field etc) or a blank slate or like theyre in a class with other people doing the same exercises. it isnt a permanent solution but even a short window of relief is better than nothing and having a reliable grounding exercise can be a massive emotional regulator